As a practical matter, it takes time for the pregnancy to develop to the point where paternity can be determined without risking the baby. I could support child support retroactive to the start of the pregnancy once paternity is established via DNA, as long as such support is null and void if the child is aborted. If the child were to be aborted after child support is received, it would have to be repaid.
Sounds like a plan to me. Too bad it will never happen.